1. Field of the Invention
The present invention relates to controlling operations for forming a band-shaped toner image onto an intermediate area residing between two toner image areas which are adjacent to each other on a surface of an image bearing member provided in an image forming apparatus, while performing an image magnification factor adjusting operation in parallel.
2. Description of Related Art
In an image forming apparatus employing an electro-photographic method, a patch toner image or a band-shaped toner image may be formed on an area (paper interval area) provided between a toner image area (defined as an area where a toner image to be transferred onto a paper sheet is formed on the basis of image data) and a next toner image area, both of which are to be provided on a surface of an image bearing member, such as a photoreceptor drum, an intermediate transfer member, etc. Hereinafter, the controlling operation for forming the patch toner image and the band-shaped toner image is referred to as a controlling operation for forming a toner zone within the paper interval area, as its generic name.
In the image forming apparatus as above-mentioned, toner is employed for the image forming operation. Further, in order to prevent the toner from deterioration caused by the result of storing the toner within a developing device for a long time, there has been well-known such a technology that the band-shaped toner image is formed on the paper interval area of the surface of the image bearing member so as to positively consume the toner. For instance, Japanese Patent Application Laid-Open Publication 2011-22468 sets forth such the toner consuming technology as abovementioned. Further, other than the band-shaped toner image, sometimes, various kinds of patch toner images may be formed for the purpose of adjusting the image forming apparatus.
In addition to the abovementioned, in the image forming apparatus, a fixing section applies heat and pressure onto the toner image, transferred onto the paper sheet, so as to fix the toner image onto the paper sheet concerned. On this occasion, the paper sheet may be shrunk under the influence of the heat applied during the fixing operation. Concretely speaking, since the image formed on the first surface of the paper sheet is already shrunk due to the fixing process, and then, the other image is formed on the second surface of the paper sheet in a shrunk state, image magnification factors of obverse and reverse sides of the paper sheet may not coincide with each other. Accordingly, when performing a duplex printing for forming images on both sides of the paper sheet, it is necessary to apply fine-adjustment processing to both the image sizes (image magnification factors) of obverse and reverse sides of the paper sheet in advance, in order to improve the accuracy of the positional relationship between the images respectively formed on obverse and reverse sides of the paper sheet.
As the controlling operation for performing the fine-adjustment between the image magnification factors of obverse and reverse sides of the paper sheet, the method for adjusting the velocity of image forming process (driving speed of the photoreceptor drum or the intermediate transfer member), the other method for adjusting the rotational velocity, etc., are well-known. In a case that such the conventional method as abovementioned is employed, it takes same time to complete the adjustment, and accordingly, a waiting time necessary for completing the adjustment (adjustment time) has been established in the conventional image forming apparatus.
Further, since the waiting time is a certain time interval residing between the toner image area and the next toner image area on the surface of the image bearing member, the waiting time may possibly overlap with the other time interval for forming the patch toner image onto the paper interval area.
In other words, sometimes, the timing for adjusting the image magnification factor would overlap with the other timing for implementing the controlling operation for forming toner zone on the paper interval area. Accordingly, there has been such a technology that the patch toner image is formed on the paper interval area after the operations for adjusting the image magnification factors of obverse and reverse sides of the paper sheet has been completed. For instance, Japanese Patent Application Laid-Open Publication 2011-100035 sets forth the abovementioned technology.